The present invention relates to a process for separating poly-.beta.-hydroxybutyrates from a biomass by extraction using liquid halogenated solvents.
Numerous micro-organisms are capable of synthesising poly-.beta.-hydroxybutyrates, the main function of which, in these micro-organisms, seems to be the storage of energy in the form of carbonaceous material. These poly-.beta.-hydroxybutyrates constitute a valuable raw material from the industrial point of view. Various techniques have already been envisaged for separating them from biomasses. Thus, it has already been proposed to extract them from the biomass using liquid halogenated solvents of low boiling point, such as chloroform and methylene chloride. In these known processes, the extraction is generally carried out at the normal boiling point of the solvent or at a lower temperature. When carried out in this way, the extraction requires very long treatment times and is accompanied by depolymerisation of the poly-.beta.-hydroxybutyrates, even though a low temperature is used.
In order to reduce the extraction times and increase the yields, it has been proposed to employ solvents, such as the cyclic carbonate of ethane-1,2-diol (ethylene carbonate) or the cyclic carbonate of propane-1,2-diol (propylene carbonate), at higher temperatures. In fact, these processes make it possible to achieve the aims, but they cause significant depolymerisation of the poly-.beta.-hydroxybutyrates.